--  @testpoint:opengauss关键字cardinality(非保留)，作为函数名
--关键字不带引号-成功
drop function if exists cardinality;
create function cardinality(i integer)
returns integer
as $$
begin
    return i+1;
end;
$$ language plpgsql;
/
--清理环境
drop function cardinality;

--关键字带双引号-成功
drop function if exists "cardinality";
create function "cardinality"(i integer)
returns integer
as $$
begin
    return i+1;
end;
$$ language plpgsql;
/
--清理环境
drop function "cardinality";

--关键字带单引号-合理报错
drop function if exists 'cardinality';
create function 'cardinality'(i integer)
returns integer
as $$
begin
    return i+1;
end;
$$ language plpgsql;
/

--关键字带反引号-合理报错
drop function if exists `cardinality`;
create function `cardinality`(i integer)
returns integer
as $$
begin
    return i+1;
end;
$$ language plpgsql;
/